Chemotype and Aggressiveness Evaluation of Fusarium graminearum and Fusarium culmorum Isolates From Wheat Fields in Wisconsin.

Fusarium graminearum commonly causes Fusarium head blight on wheat, barley, rice, and oats. F. graminearum produces nivalenol (NIV) and deoxynivalenol (DON) and forms derivatives of DON based on its acetylation sites. The fungus is profiled into chemotypes based on DON derivative chemotypes (3 acetyldeoxynivalenol [3ADON] chemotype; 15 acetyldeoxynivalenol [15ADON] chemotype), and/or the NIV chemotype. This study assessed the Fusarium population found on wheat and the chemotype profile of the isolates collected from 2016 and 2017 in Wisconsin. F. graminearum was isolated from all locations sampled in both 2016 and 2017. Fusarium culmorum was isolated only from Door County in 2016. Over both growing seasons, 91% of isolates were identified as the 15ADON chemotype, while 9% of isolates were identified as the 3ADON chemotype. Aggressiveness was quantified by area under the disease progress curve (AUDPC). The isolates with the highest AUDPC values were from the highest wheat-producing cropping districts in the state. Deoxynivalenol production in grain and sporulation and growth rate in vitro were compared with aggressiveness in the greenhouse. Our results showed that 3ADON isolates in Wisconsin were among the highest in sporulation capacity, growth rate, and DON production in grain. However, there were no significant differences in aggressiveness between the 3ADON and 15ADON isolates. The results of this research detail the baseline frequency and distribution of 3ADON and 15ADON chemotypes observed in Wisconsin. Chemotype distributions within populations of F. graminearum in Wisconsin should continue to be monitored in the future.